From: Jake Oshins <ja...@microsoft.com>

drivers:pci:hv: Update MAINTAINERS

drivers:pci:hv: New paravirtual PCI front-end for Hyper-V VMs
Signed-off-by: Jake Oshins <ja...@microsoft.com>
---
 MAINTAINERS                    |    1 +
 drivers/pci/Kconfig            |    9 +
 drivers/pci/host/Makefile      |    1 +
 drivers/pci/host/hv_pcifront.c | 2177 ++++++++++++++++++++++++++++++++++++++++
 include/linux/hyperv.h         |   18 +
 5 files changed, 2206 insertions(+)
 create mode 100644 drivers/pci/host/hv_pcifront.c

diff --git a/MAINTAINERS b/MAINTAINERS
index d8afd29..ed8d991 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4759,6 +4759,7 @@ F:        arch/x86/kernel/cpu/mshyperv.c
 F:     drivers/hid/hid-hyperv.c
 F:     drivers/hv/
 F:     drivers/input/serio/hyperv-keyboard.c
+F:     drivers/pci/host/hv_pcifront.c
 F:     drivers/net/hyperv/
 F:     drivers/scsi/storvsc_drv.c
 F:     drivers/video/fbdev/hyperv_fb.c
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 7a8f1c5..e008f68 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -114,4 +114,13 @@ config PCI_LABEL
        def_bool y if (DMI || ACPI)
        select NLS
 
+config HYPERV_VPCI
+        tristate "Hyper-V PCI Frontend"
+        depends on PCI && X86 && HYPERV
+        select PCI_HV
+        default y
+        help
+          The PCI device frontend driver allows the kernel to import arbitrary
+          PCI devices from a PCI backend to support PCI driver domains.
+
 source "drivers/pci/host/Kconfig"
diff --git a/drivers/pci/host/Makefile b/drivers/pci/host/Makefile
index f733b4e..7bf8442 100644
--- a/drivers/pci/host/Makefile
+++ b/drivers/pci/host/Makefile
@@ -2,6 +2,7 @@ obj-$(CONFIG_PCIE_DW) += pcie-designware.o
 obj-$(CONFIG_PCI_DRA7XX) += pci-dra7xx.o
 obj-$(CONFIG_PCI_EXYNOS) += pci-exynos.o
 obj-$(CONFIG_PCI_IMX6) += pci-imx6.o
+obj-$(CONFIG_HYPERV_VPCI) += hv_pcifront.o
 obj-$(CONFIG_PCI_MVEBU) += pci-mvebu.o
 obj-$(CONFIG_PCI_TEGRA) += pci-tegra.o
 obj-$(CONFIG_PCI_RCAR_GEN2) += pci-rcar-gen2.o
diff --git a/drivers/pci/host/hv_pcifront.c b/drivers/pci/host/hv_pcifront.c
new file mode 100644
index 0000000..1bdfdd5
--- /dev/null
+++ b/drivers/pci/host/hv_pcifront.c
@@ -0,0 +1,2177 @@
+/*
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Author:
+ *   Jake Oshins <ja...@microsoft.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/jiffies.h>
+#include <linux/mman.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/kthread.h>
+#include <linux/completion.h>
+#include <linux/notifier.h>
+#include <linux/of_pci.h>
+#include <linux/of_platform.h>
+#include <linux/pci.h>
+#include <linux/semaphore.h>
+
+#include <linux/hyperv.h>
+#include <asm/mshyperv.h>
+
+/*
+ * We begin with definitions supporting the Virtual PCI Express protocol
+ * with the host.
+ *
+ * Begin protocol definitions.
+ */
+
+
+/*
+ * Protocol versions. The low word is the minor version, the high word the 
major
+ * version.
+ */
+
+#define PCI_MAKE_VERSION(Major, Minor) ((__u32)(((Major) << 16) | (Minor)))
+#define PCI_MAJOR_VERSION(Version) ((__u32)(Version) >> 16)
+#define PCI_MINOR_VERSION(Version) ((__u32)(Version) & 0xff)
+
+enum {
+       PCI_PROTOCOL_VERSION_1_1 = PCI_MAKE_VERSION(1, 1),
+       PCI_PROTOCOL_VERSION_CURRENT = PCI_PROTOCOL_VERSION_1_1
+};
+
+#define PCI_CONFIG_MMIO_LENGTH 0x2000
+
+/*
+ * Message Types
+ */
+
+enum pci_message_type {
+       /*
+        * Version 1.1
+        */
+       PCI_MESSAGE_BASE                = 0x42490000,
+       PCI_BUS_RELATIONS               = PCI_MESSAGE_BASE + 0,
+       PCI_QUERY_BUS_RELATIONS         = PCI_MESSAGE_BASE + 1,
+       PCI_POWER_STATE_CHANGE          = PCI_MESSAGE_BASE + 4,
+       PCI_QUERY_RESOURCE_REQUIREMENTS = PCI_MESSAGE_BASE + 5,
+       PCI_QUERY_RESOURCE_RESOURCES    = PCI_MESSAGE_BASE + 6,
+       PCI_BUS_D0ENTRY                 = PCI_MESSAGE_BASE + 7,
+       PCI_BUS_D0EXIT                  = PCI_MESSAGE_BASE + 8,
+       PCI_READ_BLOCK                  = PCI_MESSAGE_BASE + 9,
+       PCI_WRITE_BLOCK                 = PCI_MESSAGE_BASE + 0xA,
+       PCI_EJECT                       = PCI_MESSAGE_BASE + 0xB,
+       PCI_QUERY_STOP                  = PCI_MESSAGE_BASE + 0xC,
+       PCI_REENABLE                    = PCI_MESSAGE_BASE + 0xD,
+       PCI_QUERY_STOP_FAILED           = PCI_MESSAGE_BASE + 0xE,
+       PCI_EJECTION_COMPLETE           = PCI_MESSAGE_BASE + 0xF,
+       PCI_RESOURCES_ASSIGNED          = PCI_MESSAGE_BASE + 0x10,
+       PCI_RESOURCES_RELEASED          = PCI_MESSAGE_BASE + 0x11,
+       PCI_INVALIDATE_BLOCK            = PCI_MESSAGE_BASE + 0x12,
+       PCI_QUERY_PROTOCOL_VERSION      = PCI_MESSAGE_BASE + 0x13,
+       PCI_CREATE_INTERRUPT_MESSAGE    = PCI_MESSAGE_BASE + 0x14,
+       PCI_DELETE_INTERRUPT_MESSAGE    = PCI_MESSAGE_BASE + 0x15,
+       PCI_MESSAGE_MAXIMUM
+};
+
+
+/*
+ * Structures defining the virtual PCI Express protocol.
+ */
+
+union pci_version {
+       struct {
+               __u16 minor_version;
+               __u16 major_version;
+       } parts;
+       __u32 version;
+} __packed;
+
+/*
+ * Function numbers are 8-bits wide on Express, as interpreted through ARI,
+ * which is all this driver does.
+ */
+union pci_slot_number {
+       struct {
+               __u32   func:8;
+               __u32   reserved:24;
+       } bits;
+       __u32 slot;
+} __packed;
+
+/*
+ * Pretty much as defined in the PCI Specifications.
+ */
+struct pci_function_description {
+       __u16   v_id;   /* vendor ID */
+       __u16   d_id;   /* device ID */
+       __u8    rev;
+       __u8    prog_intf;
+       __u8    subclass;
+       __u8    base_class;
+       __u32   subsystem_id;
+       union pci_slot_number s_no;
+       __u32   ser;    /* serial number */
+} __packed;
+
+/*
+ * vector - IDT entry
+ *
+ * delivery_mode - As defined in Intel's Programmer's Reference Manual, Volume
+ *  3, Chapter 8.
+ *
+ * vector_count - Number of contiguous entries in the Interrupt Descriptor
+ *  Table that are occupied by this Message-Signaled Interrupt.  For "MSI",
+ *  as first defined in PCI 2.2, this can be between 1 and 32.  For "MSI-X,"
+ *  as first defined in PCI 3.0, this must be 1, as each MSI-X table entry
+ *  would have its own descriptor.
+*/
+struct hv_msi_desc {
+       __u8    vector;
+       __u8    delivery_mode;
+       __u16   vector_count;
+       __u32   reserved;
+       __u64   proc_mask;
+} __packed;
+
+/*
+ * vector_count - same as in msi_desc
+ *
+ * data - This is the "data payload" value that is written by the device when
+ *  it generates a message-signaled interrupt, either MSI or MSI-X.
+ *
+ * address - This is the address to which the data payload is written on
+ *  interrupt generation.
+ */
+struct tran_int_desc {
+       __u16   reserved;
+       __u16   vector_count;
+       __u32   data;
+       __u64   address;
+} __packed;
+
+
+/*
+ * A generic message format for virtual PCI.
+ * Specific message formats are defined later in the file.
+ */
+
+struct pci_message {
+       __u32 message_type;
+} __packed;
+
+struct pci_child_message {
+       __u32 message_type;
+       union pci_slot_number slot;
+} __packed;
+
+struct pci_incoming_message {
+       struct vmpacket_descriptor hdr;
+       struct pci_message message_type;
+} __packed;
+
+struct pci_response {
+       struct vmpacket_descriptor hdr;
+       __s32 status; /* negative values are failures*/
+} __packed;
+
+struct pci_packet {
+       void (*completion_func)(void *context, struct pci_response *resp,
+                               int resp_packet_size);
+       void *compl_ctxt;
+       struct pci_message message;
+};
+
+/*
+ * Specific message types supporting the PCI protocol.
+ */
+
+/*
+ * Version negotiation message. Sent from the guest to the host.
+ * The guest is free to try different versions until the host
+ * accepts the version.
+ *
+ * pci_version: The protocol version requested.
+ * is_last_attempt: If TRUE, this is the last version guest will request.
+ * reservedz: Reserved field, set to zero.
+ */
+
+struct pci_version_request {
+       struct pci_message message_type;
+       enum pci_message_type protocol_version;
+} __packed;
+
+/*
+ * Bus D0 Entry.  This is sent from the guest to the host when the virtual
+ * bus (PCI Express port) is ready for action.
+ */
+
+struct pci_bus_d0_entry {
+       struct pci_message message_type;
+       __u32 reserved;
+       __u64 mmio_base;
+} __packed;
+
+
+struct pci_bus_relations {
+       struct pci_incoming_message incoming;
+       __u32 device_count;
+       struct pci_function_description func[1];
+} __packed;
+
+struct pci_q_res_req_response {
+       struct vmpacket_descriptor hdr;
+       __s32 status; /* negative values are failures*/
+       __u32 probed_bar[6];
+} __packed;
+
+struct pci_set_power {
+       struct pci_message message_type;
+       union pci_slot_number slot;
+       __u32 power_state; /* In Windows terms */
+       __u32 reserved;
+} __packed;
+
+
+struct pci_set_power_response {
+       struct vmpacket_descriptor hdr;
+       __s32 status; /* negative values are failures*/
+       union pci_slot_number slot;
+       __u32 resultant_state;  /* In Windows terms */
+       __u32 reserved;
+} __packed;
+
+struct pci_resources_assigned {
+       struct pci_message message_type;
+       union pci_slot_number slot;
+       u8 memory_range[0x14][6]; /* not used here */
+       u32 msi_descriptors;
+       u32 reserved[4];
+} __packed;
+
+struct pci_create_interrupt {
+       struct pci_message message_type;
+       union pci_slot_number slot;
+       struct hv_msi_desc int_desc;
+} __packed;
+
+struct pci_create_int_response {
+       struct pci_response response;
+       u32 reserved;
+       struct tran_int_desc int_desc;
+} __packed;
+
+struct pci_delete_interrupt {
+       struct pci_message message_type;
+       union pci_slot_number slot;
+       struct tran_int_desc int_desc;
+} __packed;
+
+struct pci_read_block {
+       struct pci_message message_type;
+       int block_id;
+       union pci_slot_number slot;
+       int bytes_requested;
+} __packed;
+
+struct pci_write_block {
+       struct pci_message message_type;
+       int block_id;
+       union pci_slot_number slot;
+       int byte_count;
+       unsigned char bytes[CONFIG_BLOCK_SIZE_MAX];
+} __packed;
+
+struct pci_dev_inval_block {
+       struct pci_incoming_message incoming;
+       union pci_slot_number slot;
+       u64 block_mask;
+} __packed;
+
+struct pci_dev_incoming {
+       struct pci_incoming_message incoming;
+       union pci_slot_number slot;
+} __packed;
+
+struct pci_eject_response {
+       u32 message_type;
+       union pci_slot_number slot;
+       u32 status;
+} __packed;
+
+static int pci_ring_size = (4 * PAGE_SIZE);
+
+/*
+ * Driver specific state.
+ */
+
+enum hv_pcibus_state {
+       hv_pcibus_init = 0,
+       hv_pcibus_probed,
+       hv_pcibus_installed,
+       hv_pcibus_maximum
+};
+
+struct hv_pcibus_device {
+       struct pci_sysdata sysdata;
+       enum hv_pcibus_state state;
+       atomic_t remove_lock;
+       struct hv_device *hdev;
+       resource_size_t low_mmio_space;
+       resource_size_t high_mmio_space;
+       struct resource *mem_config;
+       struct resource *low_mmio_res;
+       struct resource *high_mmio_res;
+       struct completion *survey_event;
+       struct completion remove_event;
+       struct pci_bus *pci_bus;
+       spinlock_t config_lock;
+       spinlock_t device_list_lock;
+       void __iomem *cfg_addr;
+
+       struct semaphore enum_sem;
+       struct list_head resources_for_children;
+
+       /* Lists protected by device_list_lock */
+       struct list_head children;
+       struct list_head dr_list;
+       struct work_struct wrk;
+};
+
+/* Tracks "Device Relations" messages from the host, which must be both
+   processed in order and deferred so that they don't run in the context
+   of the incoming packet callback. */
+struct hv_dr_work {
+       struct work_struct wrk;
+       struct hv_pcibus_device *bus;
+};
+
+struct hv_dr_state {
+       struct list_head list_entry;
+       __u32 device_count;
+       struct pci_function_description func[1];
+};
+
+enum hv_pcichild_state {
+       hv_pcichild_init = 0,
+       hv_pcichild_requirements,
+       hv_pcichild_resourced,
+       hv_pcichild_ejecting,
+       hv_pcichild_maximum
+};
+
+enum hv_pcidev_ref_reason {
+       hv_pcidev_ref_invalid = 0,
+       hv_pcidev_ref_initial,
+       hv_pcidev_ref_by_slot,
+       hv_pcidev_ref_packet,
+       hv_pcidev_ref_pnp,
+       hv_pcidev_ref_childlist,
+       hv_pcidev_ref_max
+};
+
+static char *hv_pcidev_ref_debug[hv_pcidev_ref_max] = {
+       "hv_pcidev_ref_invalid",
+       "hv_pcidev_ref_initial",
+       "hv_pcidev_ref_by_slot",
+       "hv_pcidev_ref_packet",
+       "hv_pcidev_ref_pnp",
+       "hv_pcidev_ref_childlist"
+};
+
+struct hv_pci_dev {
+       /* List protected by pci_rescan_remove_lock */
+       struct list_head list_entry;
+       atomic_t refs;
+       enum hv_pcichild_state state;
+       /* What would be observed if one wrote 0xFFFFFFFF to a BAR and then
+          read it back, for each of the BAR offsets within config space. */
+       u32 probed_bar[6];
+       struct pci_function_description desc;
+       bool reported_missing;
+       struct hv_pcibus_device *hbus;
+       struct work_struct wrk;
+       void (*block_invalidate)(void *context, u64 block_mask);
+       void *invalidate_context;
+};
+
+struct hv_pci_compl {
+       struct completion host_event;
+       __s32 completion_status;
+};
+
+struct x86_msi_ops hv_msi;
+
+/**
+ * This function is used to trigger an event and report status
+ * for any message for which the completion packet contains a
+ * status and nothing else.
+ *
+ * @param context - Set up by the sender of the packet.
+ * @param resp - The response packet
+ * @param resp_packet_size - Size in bytes of the packet
+ */
+static
+void
+hv_pci_generic_compl(void *context, struct pci_response *resp,
+                    int resp_packet_size)
+{
+       struct hv_pci_compl *comp_pkt = (struct hv_pci_compl *)context;
+
+       if (resp_packet_size >= offsetofend(struct pci_response, status))
+               comp_pkt->completion_status = resp->status;
+       complete(&comp_pkt->host_event);
+}
+
+static struct hv_pci_dev *lookup_hv_pcidev(struct hv_pcibus_device *hbus,
+                                          u32 slot);
+static void hv_pcichild_inc(struct hv_pci_dev *hv_pcidev,
+                           enum hv_pcidev_ref_reason reason);
+static void hv_pcichild_dec(struct hv_pci_dev *hv_pcidev,
+                           enum hv_pcidev_ref_reason reason);
+
+static void hv_pcibus_inc(struct hv_pcibus_device *hv_pcibus);
+static void hv_pcibus_dec(struct hv_pcibus_device *hv_pcibus);
+
+/**
+ * Windows uses a slightly different representation of PCI slot.
+ *  These helper functions convert between what's sent in the
+ *  protocol messages and what's used in Linux.
+ *
+ * @param devfn - The Linux representation of PCI slot
+ *
+ * @return u32 - The Windows representation
+ */
+static u32 devfn_to_slot(int devfn)
+{
+       union pci_slot_number slot;
+
+       slot.slot = 0;
+       slot.bits.func = PCI_SLOT(devfn) | (PCI_FUNC(devfn) << 5);
+
+       return slot.slot;
+}
+
+static int slot_to_devfn(u32 slot)
+{
+       union pci_slot_number slot_no;
+
+       slot_no.slot = slot;
+       return PCI_DEVFN(0, slot_no.bits.func);
+}
+
+/**
+ * These internal functions read and write config space for a
+ * PCI device.
+ *
+ * @param hpdev - The PCI driver's representation of the device
+ * @param where - Offset within config space
+ * @param size - Size of the transfer
+ * @param val - The data being transferred
+ */
+static void _hv_pcifront_read_config(struct hv_pci_dev *hpdev, int where,
+                                    int size, u32 *val)
+{
+       unsigned long flags;
+       void __iomem *addr = ((u8 *)hpdev->hbus->cfg_addr) + 0x1000 + where;
+
+       /*
+        * If the attempt is to read the IDs or the ROM BAR, simulate that.
+        */
+       if (where + size <= PCI_COMMAND) {
+
+               memcpy(val, ((u8 *)&(hpdev->desc.v_id)) + where, size);
+
+       } else if (where >= PCI_CLASS_REVISION && where + size <=
+                  PCI_CACHE_LINE_SIZE) {
+
+               memcpy(val, ((u8 *)&(hpdev->desc.rev)) + where -
+                      PCI_CLASS_REVISION, size);
+
+       } else if (where >= PCI_SUBSYSTEM_VENDOR_ID && where + size <=
+                  PCI_ROM_ADDRESS) {
+
+               memcpy(val, (u8 *)&hpdev->desc.subsystem_id + where -
+                      PCI_SUBSYSTEM_VENDOR_ID, size);
+
+       } else if (where >= PCI_ROM_ADDRESS && where + size <=
+                  PCI_CAPABILITY_LIST) {
+
+               /* ROM BARs are unimplemented */
+               *val = 0;
+
+       } else if (where >= PCI_INTERRUPT_LINE && where + size <=
+                  PCI_INTERRUPT_PIN) {
+
+               /*
+                * Interrupt Line and Interrupt PIN are hard-wired to zero
+                * because this front-end only supports message-signaled
+                * interrupts.
+                */
+               *val = 0;
+
+       } else {
+               spin_lock_irqsave(&hpdev->hbus->config_lock, flags);
+               writel(hpdev->desc.s_no.slot, hpdev->hbus->cfg_addr);
+               switch (size) {
+               case 1:
+                       *val = readb(addr);
+                       break;
+               case 2:
+                       *val = readw(addr);
+                       break;
+               default:
+                       *val = readl(addr);
+                       break;
+               }
+               spin_unlock_irqrestore(&hpdev->hbus->config_lock, flags);
+       }
+
+}
+
+static void _hv_pcifront_write_config(struct hv_pci_dev *hpdev, int where,
+                                     int size, u32 val)
+{
+       unsigned long flags;
+       void __iomem *addr = ((__u8 *)hpdev->hbus->cfg_addr) + 0x1000 + where;
+
+       if (where >= PCI_SUBSYSTEM_VENDOR_ID &&
+           where + size <= PCI_CAPABILITY_LIST) {
+
+               /* SSIDs and ROM BARs are read-only */
+
+       } else if (where >= PCI_COMMAND) {
+               spin_lock_irqsave(&hpdev->hbus->config_lock, flags);
+               writel(hpdev->desc.s_no.slot, hpdev->hbus->cfg_addr);
+               switch (size) {
+               case 1:
+                       writeb(val, addr);
+                       break;
+               case 2:
+                       writew(val, addr);
+                       break;
+               default:
+                       writel(val, addr);
+                       break;
+               }
+               spin_unlock_irqrestore(&hpdev->hbus->config_lock, flags);
+       }
+}
+
+/**
+ * hv_pcifront_read_config - Read configuration space
+ * @bus: PCI Bus structure
+ * @devfn: Device/function
+ * @where: Offset from base
+ * @size: Byte/word/dword
+ * @val: Value to be read
+ *
+ * Return: PCIBIOS_SUCCESSFUL on success
+ *        PCIBIOS_DEVICE_NOT_FOUND on failure
+ */
+static int hv_pcifront_read_config(struct pci_bus *bus, unsigned int devfn,
+                                  int where, int size, u32 *val)
+{
+       struct hv_pcibus_device *hbus =
+               container_of(bus->sysdata, struct hv_pcibus_device, sysdata);
+       struct hv_pci_dev *hpdev = NULL;
+
+       hpdev = lookup_hv_pcidev(hbus, devfn_to_slot(devfn));
+       if (!hpdev)
+               return PCIBIOS_DEVICE_NOT_FOUND;
+
+       _hv_pcifront_read_config(hpdev, where, size, val);
+
+       hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+       return PCIBIOS_SUCCESSFUL;
+}
+
+/**
+ * hv_pcifront_write_config - Write configuration space
+ * @bus: PCI Bus structure
+ * @devfn: Device/function
+ * @where: Offset from base
+ * @size: Byte/word/dword
+ * @val: Value to be written to device
+ *
+ * Return: PCIBIOS_SUCCESSFUL on success
+ *        PCIBIOS_DEVICE_NOT_FOUND on failure
+ */
+static int hv_pcifront_write_config(struct pci_bus *bus, unsigned int devfn,
+                                   int where, int size, u32 val)
+{
+       struct hv_pcibus_device *hbus =
+           container_of(bus->sysdata, struct hv_pcibus_device, sysdata);
+       struct hv_pci_dev *hpdev = NULL;
+
+       hpdev = lookup_hv_pcidev(hbus, devfn_to_slot(devfn));
+       if (!hpdev)
+               return PCIBIOS_DEVICE_NOT_FOUND;
+
+       _hv_pcifront_write_config(hpdev, where, size, val);
+
+       hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+       return PCIBIOS_SUCCESSFUL;
+}
+
+/* PCIe operations */
+static struct pci_ops hv_pcifront_ops = {
+       .read  = hv_pcifront_read_config,
+       .write = hv_pcifront_write_config,
+};
+
+/*
+ * Paravirtual backchannel
+ *
+ * Windows SR-IOV provides a backchannel mechanism in software for 
communication
+ * between a VF driver and a PF driver.  These "configuration blocks" are
+ * similar in concept to PCI configuration space, but instead of doing reads 
and
+ * writes in 32-bit chunks through a very slow path, packets of up to 128 bytes
+ * can be sent or received asynchronously.
+ *
+ * Nearly every SR-IOV device contains just such a communications channel in
+ * hardware, so using this one in software is usually optional.  Using the
+ * software channel, however, allows driver implementers to leverage software
+ * tools that fuzz the communications channel looking for vulnerabilities.
+ *
+ * The usage model for these packets puts the responsibility for reading or
+ * writing on the VF driver.  The VF driver sends a read or a write packet,
+ * indicating which "block" is being referred to by number.
+ *
+ * If the PF driver wishes to initiate communication, it can "invalidate" one 
or
+ * more of the first 64 blocks.  This invalidation is delivered via a callback
+ * supplied by the VF driver by this driver.
+ *
+ * No protocol is implied, except that supplied by the PF and VF drivers.
+ */
+
+struct hv_read_config_compl {
+       struct hv_pci_compl gen_compl;
+       void *buf;
+       int len;
+       int bytes_returned;
+};
+
+static
+void
+hv_pci_read_config_compl(void *context, struct pci_response *resp,
+                        int resp_packet_size)
+{
+       struct hv_read_config_compl *comp_pkt =
+               (struct hv_read_config_compl *)context;
+       int data_len;
+       void *data;
+
+       data_len = resp_packet_size - offsetof(struct pci_response, status);
+
+       if (data_len > 0) {
+               data = ((char *)resp) + offsetof(struct pci_response, status);
+               memcpy(comp_pkt->buf, data, max(comp_pkt->len, data_len));
+       }
+       comp_pkt->bytes_returned = data_len;
+       complete(&comp_pkt->gen_compl.host_event);
+}
+
+int hv_read_config_block(struct pci_dev *pdev, void *buf, int buf_len,
+                        int block_id, int *bytes_returned)
+{
+       struct hv_pcibus_device *hbus =
+               container_of(pdev->bus->sysdata, struct hv_pcibus_device,
+                            sysdata);
+       struct {
+               struct pci_packet pkt;
+               char buf[sizeof(struct pci_read_block) -
+                        offsetof(struct pci_packet, message)];
+       } pkt;
+       struct hv_read_config_compl comp_pkt;
+       struct pci_read_block *read_blk;
+       int ret;
+
+       if (buf_len > CONFIG_BLOCK_SIZE_MAX)
+               return -ENOSPC;
+
+       memset(&pkt, 0, sizeof(pkt));
+       init_completion(&comp_pkt.gen_compl.host_event);
+       pkt.pkt.completion_func = hv_pci_read_config_compl;
+       pkt.pkt.compl_ctxt = &comp_pkt;
+       read_blk = (struct pci_read_block *)&pkt.pkt.message;
+       read_blk->message_type.message_type = PCI_READ_BLOCK;
+       read_blk->slot.slot = devfn_to_slot(pdev->devfn);
+       read_blk->bytes_requested = buf_len;
+
+       ret = vmbus_sendpacket(hbus->hdev->channel, &pkt, sizeof(pkt),
+                              (unsigned long)&comp_pkt, VM_PKT_DATA_INBAND,
+                              VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+       if (!ret) {
+               wait_for_completion(&comp_pkt.gen_compl.host_event);
+               *bytes_returned = comp_pkt.bytes_returned;
+       }
+
+       return ret;
+}
+EXPORT_SYMBOL(hv_read_config_block);
+
+int hv_write_config_block(struct pci_dev *pdev, void *buf, int len,
+                         int block_id)
+{
+       struct hv_pcibus_device *hbus =
+               container_of(pdev->bus->sysdata, struct hv_pcibus_device,
+                            sysdata);
+       struct {
+               struct pci_packet pkt;
+               char buf[sizeof(struct pci_write_block) -
+                        offsetof(struct pci_packet, message)];
+       } pkt;
+       struct hv_pci_compl comp_pkt;
+       struct pci_write_block *write_blk;
+       u32 pkt_size;
+       int ret;
+
+       if (len > CONFIG_BLOCK_SIZE_MAX)
+               return -ENOSPC;
+
+       memset(&pkt, 0, sizeof(pkt));
+       init_completion(&comp_pkt.host_event);
+       pkt.pkt.completion_func = hv_pci_generic_compl;
+       pkt.pkt.compl_ctxt = &comp_pkt;
+       write_blk = (struct pci_write_block *)&pkt.pkt.message;
+       write_blk->message_type.message_type = PCI_WRITE_BLOCK;
+       write_blk->slot.slot = devfn_to_slot(pdev->devfn);
+       write_blk->byte_count = len;
+       memcpy(write_blk->bytes, buf, len);
+       pkt_size = offsetof(struct pci_write_block, bytes) + len;
+
+       ret = vmbus_sendpacket(hbus->hdev->channel, &pkt, pkt_size,
+                              (unsigned long)&pkt.pkt, VM_PKT_DATA_INBAND,
+                              VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+       if (!ret)
+               wait_for_completion(&comp_pkt.host_event);
+
+       return ret;
+}
+EXPORT_SYMBOL(hv_write_config_block);
+
+int hv_register_block_invalidate(struct pci_dev *pdev, void *context,
+                                void (*block_invalidate)(void *context,
+                                                        u64 block_mask))
+{
+       struct hv_pcibus_device *hbus =
+               container_of(pdev->bus->sysdata, struct hv_pcibus_device,
+                            sysdata);
+       struct hv_pci_dev *hpdev;
+
+       hpdev = lookup_hv_pcidev(hbus, devfn_to_slot(pdev->devfn));
+       if (!hpdev)
+               return -ENODEV;
+
+       hpdev->block_invalidate = block_invalidate;
+       hpdev->invalidate_context = context;
+
+       hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+       return 0;
+
+}
+EXPORT_SYMBOL(hv_register_block_invalidate);
+
+/* Interrupt management hooks */
+
+int hv_set_affinity(struct irq_data *data, const struct cpumask *dest,
+                   bool force)
+{
+       return 0;
+}
+
+int hv_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
+{
+       struct msi_desc *msidesc;
+       struct irq_chip *chip;
+       int ret;
+
+       /*
+        * Call the base function which will do everything related to setting up
+        * the tracking structures.
+        */
+
+       ret = hv_msi.setup_msi_irqs(pdev, nvec, type);
+       if (ret)
+               return ret;
+
+       list_for_each_entry(msidesc, &pdev->msi_list, list) {
+               if (msidesc->irq) {
+                       chip = irq_get_chip(msidesc->irq);
+                       /*
+                        * Replace the affinity callback so that it doesn't
+                        * rearrage the message in the hardware.
+                        */
+                       chip->irq_set_affinity = hv_set_affinity;
+               }
+       }
+
+       return 0;
+}
+
+struct compose_comp_ctxt {
+       struct hv_pci_compl comp_pkt;
+       struct tran_int_desc int_desc;
+};
+
+static
+void
+hv_pci_compose_compl(void *context, struct pci_response *resp,
+                    int resp_packet_size)
+{
+       struct compose_comp_ctxt *comp_pkt =
+               (struct compose_comp_ctxt *)context;
+       struct pci_create_int_response *int_resp =
+               (struct pci_create_int_response *)resp;
+
+       comp_pkt->comp_pkt.completion_status = resp->status;
+       comp_pkt->int_desc = int_resp->int_desc;
+       complete(&comp_pkt->comp_pkt.host_event);
+}
+
+void hv_compose_msi_msg(struct pci_dev *pdev, unsigned int irq,
+                       unsigned int dest, struct msi_msg *msg, u8 hpet_id)
+{
+       struct irq_cfg *cfg = irq_get_chip_data(irq);
+       struct hv_pci_dev *hpdev = NULL;
+       struct pci_create_interrupt *int_pkt;
+       struct compose_comp_ctxt comp;
+       struct {
+               struct pci_packet pkt;
+               u8 buffer[sizeof(struct pci_create_interrupt) -
+                         sizeof(struct pci_message)];
+       } ctxt;
+       struct hv_pcibus_device *hbus =
+               container_of(pdev->bus->sysdata, struct hv_pcibus_device,
+                            sysdata);
+       int cpu;
+       int ret;
+
+       hpdev = lookup_hv_pcidev(hbus, devfn_to_slot(pdev->devfn));
+       if (!hpdev)
+               return;
+
+       memset(&ctxt, 0, sizeof(ctxt));
+       init_completion(&comp.comp_pkt.host_event);
+       ctxt.pkt.completion_func = hv_pci_compose_compl;
+       ctxt.pkt.compl_ctxt = &comp;
+       int_pkt = (struct pci_create_interrupt *)&ctxt.pkt.message;
+       int_pkt->message_type.message_type = PCI_CREATE_INTERRUPT_MESSAGE;
+       int_pkt->slot.slot = hpdev->desc.s_no.slot;
+       int_pkt->int_desc.vector = cfg->vector;
+       int_pkt->int_desc.vector_count = 1;
+       int_pkt->int_desc.delivery_mode =
+               (apic->irq_delivery_mode == dest_LowestPrio) ? 1 : 0;
+       for_each_cpu(cpu, cfg->domain)
+               int_pkt->int_desc.proc_mask |=
+               (1 << vmbus_procnum_to_vpnum(cpu));
+
+       ret = vmbus_sendpacket(hbus->hdev->channel, int_pkt, sizeof(*int_pkt),
+                              (unsigned long)&ctxt.pkt, VM_PKT_DATA_INBAND,
+                              VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+       if (!ret)
+               wait_for_completion(&comp.comp_pkt.host_event);
+
+       if (comp.comp_pkt.completion_status < 0) {
+               pr_err("Request for interrupt failed: 0x%x",
+                      comp.comp_pkt.completion_status);
+               msg->address_hi = 0;
+               msg->address_lo = 0;
+               msg->data = 0;
+       } else {
+               msg->address_hi = comp.int_desc.address >> 32;
+               msg->address_lo = comp.int_desc.address & 0xffffffff;
+               msg->data = comp.int_desc.data;
+       }
+
+       hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+}
+
+void hv_teardown_msi_irqs(struct pci_dev *pdev)
+{
+       struct hv_pci_dev *hpdev = NULL;
+       struct pci_delete_interrupt *int_pkt;
+       struct msi_desc *msidesc;
+       struct {
+               struct pci_packet pkt;
+               u8 buffer[sizeof(struct pci_delete_interrupt) -
+                         sizeof(struct pci_message)];
+       } ctxt;
+       struct hv_pcibus_device *hbus =
+               container_of(pdev->bus->sysdata, struct hv_pcibus_device,
+                            sysdata);
+
+       hpdev = lookup_hv_pcidev(hbus, devfn_to_slot(pdev->devfn));
+
+       list_for_each_entry(msidesc, &pdev->msi_list, list) {
+               memset(&ctxt, 0, sizeof(ctxt));
+               int_pkt = (struct pci_delete_interrupt *)&ctxt.pkt.message;
+               int_pkt->message_type.message_type =
+                       PCI_DELETE_INTERRUPT_MESSAGE;
+               int_pkt->slot.slot = hpdev->desc.s_no.slot;
+               int_pkt->int_desc.address = (u64)msidesc->msg.address_hi << 32 |
+                                           msidesc->msg.address_lo;
+               int_pkt->int_desc.data = msidesc->msg.data;
+               vmbus_sendpacket(hbus->hdev->channel, int_pkt, sizeof(*int_pkt),
+                                (unsigned long)&ctxt.pkt, VM_PKT_DATA_INBAND,
+                                0);
+       }
+
+       hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+       hv_msi.teardown_msi_irqs(pdev);
+}
+
+void hv_restore_msi_irqs(struct pci_dev *pdev)
+{
+       hv_msi.restore_msi_irqs(pdev);
+}
+
+static void survey_child_resources(struct hv_pcibus_device *hbus)
+{
+       struct list_head *iter;
+       struct hv_pci_dev *hpdev;
+       resource_size_t bar_size = 0;
+       unsigned long flags;
+       struct completion *event;
+       u64 bar_val;
+       int i;
+
+       /* If nobody is waiting on the answer, don't compute it. */
+       event = xchg(&hbus->survey_event, NULL);
+       if (!event)
+               return;
+
+       /* If the answer has already been computed, go with it. */
+       if (hbus->low_mmio_space || hbus->high_mmio_space) {
+               complete(event);
+               return;
+       }
+
+       spin_lock_irqsave(&hbus->device_list_lock, flags);
+
+       /*
+        * Due to an interesting quirk of the PCI spec, all memory regions
+        * for a child device are a power of 2 in size and aligned in memory,
+        * so it's sufficient to just add them up without tracking alignment.
+        */
+       list_for_each(iter, &hbus->children) {
+               hpdev = container_of(iter, struct hv_pci_dev, list_entry);
+               for (i = 0; i < 6; i++) {
+                       if (hpdev->probed_bar[i] & PCI_BASE_ADDRESS_SPACE_IO)
+                               pr_err("There's an I/O BAR in this list!\n");
+
+                       if (hpdev->probed_bar[i] != 0) {
+                               /*
+                                * A probed BAR has all the upper bits set that
+                                * can be changed.
+                                */
+
+                               bar_val = hpdev->probed_bar[i];
+                               pr_devel("bar_val: 0x%llx\n", bar_val);
+                               if (bar_val & PCI_BASE_ADDRESS_MEM_TYPE_64)
+                                       bar_val |=
+                                       ((u64)hpdev->probed_bar[++i] << 32);
+                               else
+                                       bar_val |= 0xffffffff00000000ULL;
+
+                               bar_size = 1 +
+                                       ~(bar_val & PCI_BASE_ADDRESS_MEM_MASK);
+                               pr_devel("bar_size: 0x%llx\n", bar_size);
+
+                               if (bar_val & PCI_BASE_ADDRESS_MEM_TYPE_64)
+                                       hbus->high_mmio_space += bar_size;
+                               else
+                                       hbus->low_mmio_space += bar_size;
+                       }
+               }
+       }
+
+       spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+       pr_devel("high_mmio_space: 0x%llx  low_mmio_space: 0x%llx\n",
+                hbus->high_mmio_space, hbus->low_mmio_space);
+
+       complete(event);
+}
+
+/**
+ * The core PCI driver code seems much, much happier if the BARs
+ * for a device have values upon first scan.  So fill them in.
+ * The algorithm below works down from large sizes to small,
+ * attempting to pack the assignments optimally.  The
+ * assumption, enforced in other parts of the code, is that the
+ * beginning of the memory-mapped I/O space will be aligned on
+ * the largest BAR size.
+ */
+static void prepopulate_bars(struct hv_pcibus_device *hbus)
+{
+       resource_size_t high_bar_size = 0;
+       resource_size_t low_bar_size = 0;
+       resource_size_t high_base = 0;
+       resource_size_t low_base = 0;
+       resource_size_t bar_size;
+       struct hv_pci_dev *hpdev;
+       struct list_head *iter;
+       unsigned long flags;
+       u64 bar_val;
+       u32 command;
+       bool high;
+       int i;
+
+       if (hbus->low_mmio_space) {
+               low_bar_size = 1<<(63-__builtin_clzll(hbus->low_mmio_space));
+               low_base = hbus->low_mmio_res->start;
+       }
+
+       if (hbus->high_mmio_space) {
+               high_bar_size = 1<<(63-__builtin_clzll(hbus->high_mmio_space));
+               high_base = hbus->high_mmio_res->start;
+       }
+
+       spin_lock_irqsave(&hbus->device_list_lock, flags);
+
+       /* Pick addresses for the BARs. */
+       do {
+               list_for_each(iter, &hbus->children) {
+                       hpdev = container_of(iter, struct hv_pci_dev,
+                                            list_entry);
+
+                       for (i = 0; i < 6; i++) {
+
+                               bar_val = hpdev->probed_bar[i];
+                               if (bar_val == 0)
+                                       continue;
+
+                               high = bar_val & PCI_BASE_ADDRESS_MEM_TYPE_64;
+                               if (high)
+                                       bar_val |=
+                                           ((u64)hpdev->probed_bar[i+1] << 32);
+                               else
+                                       bar_val |= 0xffffffffULL << 32;
+
+                               bar_size = 1ULL +
+                                       ~(bar_val & PCI_BASE_ADDRESS_MEM_MASK);
+
+                               if (high) {
+
+                                       if (high_bar_size != bar_size) {
+                                               i++;
+                                               continue;
+                                       }
+
+                                       _hv_pcifront_write_config(hpdev,
+                                               PCI_BASE_ADDRESS_0 + (4 * i),
+                                               4,
+                                               (u32)(high_base & 0xffffff00));
+                                       _hv_pcifront_write_config(hpdev,
+                                               PCI_BASE_ADDRESS_0 +
+                                                                 (4 * (i + 1)),
+                                               4, (u32)(high_base >> 32));
+
+                                       high_base += bar_size;
+                               } else {
+                                       if (low_bar_size != bar_size)
+                                               continue;
+
+                                       _hv_pcifront_write_config(hpdev,
+                                               PCI_BASE_ADDRESS_0 + (4 * i),
+                                               4,
+                                               (u32)(low_base & 0xffffff00));
+                                       low_base += bar_size;
+                               }
+                       }
+
+                       if ((high_bar_size <= 1) && (low_bar_size <= 1)) {
+                               /* Set the memory enable bit. */
+                               _hv_pcifront_read_config(hpdev, PCI_COMMAND, 2,
+                                                        &command);
+                               command |= PCI_COMMAND_MEMORY;
+                               _hv_pcifront_write_config(hpdev, PCI_COMMAND, 2,
+                                                         command);
+                               break;
+                       }
+               }
+
+               high_bar_size >>= 1;
+               low_bar_size >>= 1;
+       }  while (high_bar_size || low_bar_size);
+
+       spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+}
+
+static int create_root_hv_pci_bus(struct hv_pcibus_device *hbus)
+{
+       /* Register the device */
+       hbus->pci_bus = pci_create_root_bus(&hbus->hdev->device,
+                                           0, /* bus number is always zero */
+                                           &hv_pcifront_ops,
+                                           &hbus->sysdata,
+                                           &hbus->resources_for_children);
+       if (!hbus->pci_bus)
+               return -ENODEV;
+
+       pci_scan_child_bus(hbus->pci_bus);
+       pci_bus_assign_resources(hbus->pci_bus);
+       pci_bus_add_devices(hbus->pci_bus);
+       hbus->state = hv_pcibus_installed;
+       return 0;
+}
+
+struct q_res_req_compl {
+       struct completion host_event;
+       struct hv_pci_dev *hpdev;
+};
+
+/**
+ * This function is invoked on completion of a Query Resource
+ * Requirements packet.
+ *
+ * @param context - The completion context.
+ * @param resp - The respose that came from the host.
+ * @param resp_packet_size - The size in bytes of resp.
+ */
+static void q_resource_requirements(void *context, struct pci_response *resp,
+                                   int resp_packet_size)
+{
+       struct q_res_req_compl *completion = (struct q_res_req_compl *)context;
+       struct pci_q_res_req_response *q_res_req =
+               (struct pci_q_res_req_response *)resp;
+       int i;
+
+       if (resp->status < 0) {
+               pr_err("query resource requirements failed: %x\n",
+                      resp->status);
+       } else {
+               for (i = 0; i < 6; i++) {
+                       completion->hpdev->probed_bar[i] =
+                               q_res_req->probed_bar[i];
+                       pr_devel("BAR[%d]: %08x\n", i,
+                                q_res_req->probed_bar[i]);
+               }
+       }
+
+       complete(&completion->host_event);
+}
+
+static void hv_pcichild_inc(struct hv_pci_dev *hpdev,
+                           enum hv_pcidev_ref_reason reason)
+{
+       pr_devel("+%s %p\n", hv_pcidev_ref_debug[reason], hpdev);
+       atomic_inc(&hpdev->refs);
+}
+
+static void hv_pcichild_dec(struct hv_pci_dev *hpdev,
+                           enum hv_pcidev_ref_reason reason)
+{
+       pr_devel("-%s %p\n", hv_pcidev_ref_debug[reason], hpdev);
+       if (atomic_dec_and_test(&hpdev->refs)) {
+               pr_devel("Freeing hv_pcidev %p\n", hpdev);
+               kfree(hpdev);
+       }
+}
+
+/**
+ * This function creates the tracking structure for a new child
+ * device and kicks off the process of figuring out what it is.
+ *
+ * @param hbus - The internal struct tracking this root PCI bus.
+ * @param desc - The information supplied so far from the host
+ *             about the device.
+ *
+ * @return struct hv_pci_dev*
+ */
+static
+struct hv_pci_dev *
+new_pcichild_device(struct hv_pcibus_device *hbus,
+                   struct pci_function_description *desc)
+{
+       struct hv_pci_dev *hpdev = NULL;
+       struct pci_child_message *res_req;
+       struct q_res_req_compl comp_pkt;
+       union {
+       struct pci_packet init_packet;
+               __u8 buffer[0x100];
+       } pkt;
+       unsigned long flags;
+       int ret;
+
+       hpdev = kzalloc(sizeof(struct hv_pci_dev), GFP_ATOMIC);
+       if (!hpdev)
+               return NULL;
+
+       pr_devel("New child device (%p) reported (%04x:%04x) in slot %x.\n",
+                hpdev, desc->v_id, desc->d_id, desc->s_no.slot);
+
+       hpdev->hbus = hbus;
+
+       memset(&pkt, 0, sizeof(pkt));
+       init_completion(&comp_pkt.host_event);
+       comp_pkt.hpdev = hpdev;
+       pkt.init_packet.compl_ctxt = &comp_pkt;
+       pkt.init_packet.completion_func = q_resource_requirements;
+       res_req = (struct pci_child_message *)&pkt.init_packet.message;
+       res_req->message_type = PCI_QUERY_RESOURCE_REQUIREMENTS;
+       res_req->slot.slot = desc->s_no.slot;
+
+       ret = vmbus_sendpacket(hbus->hdev->channel, res_req,
+                           sizeof(struct pci_child_message),
+                           (unsigned long)&pkt.init_packet,
+                           VM_PKT_DATA_INBAND,
+                           VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+       if (ret)
+               goto new_pcichild_device_error;
+
+       wait_for_completion(&comp_pkt.host_event);
+
+       hpdev->desc = *desc;
+       hv_pcichild_inc(hpdev, hv_pcidev_ref_initial);
+       hv_pcichild_inc(hpdev, hv_pcidev_ref_childlist);
+       spin_lock_irqsave(&hbus->device_list_lock, flags);
+       list_add_tail(&hpdev->list_entry, &hbus->children);
+       spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+       return hpdev;
+
+new_pcichild_device_error:
+
+       kfree(hpdev);
+       return NULL;
+}
+
+static struct hv_pci_dev *lookup_hv_pcidev(struct hv_pcibus_device *hbus,
+                                          u32 slot)
+{
+       unsigned long flags;
+       struct hv_pci_dev *iter, *hpdev = NULL;
+
+       spin_lock_irqsave(&hbus->device_list_lock, flags);
+       list_for_each_entry(iter, &hbus->children, list_entry) {
+               if (iter->desc.s_no.slot == slot) {
+                       hpdev = iter;
+                       hv_pcichild_inc(hpdev, hv_pcidev_ref_by_slot);
+                       break;
+               }
+       }
+       spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+       return hpdev;
+}
+
+/**
+ * "Bus Relations" is the Windows term for "children of this bus."  The
+ * terminology is preserved here for people trying to debug the interaction
+ * between Hyper-V and Linux.  This function is called when the parent 
partition
+ * reports a list of functions that should be observed under this PCI Express
+ * port (bus).
+ *
+ * This function updates the list, and must tolerate being called multiple 
times
+ * with the same information.  The typical number of child devices is one,
+ * with very atypical cases involving three or four, so the algorithms used 
here
+ * can be simple and inefficient.
+ *
+ * It must also treat the omission of a previously observed device as
+ * notification that the device no longer exists.
+ *
+ * Note that this function is a work item, and it may not be
+ * invoked in the order that the host sent it.  Back to back
+ * updates of the list of present devices may involve queuing
+ * mulitple work items, and this one may run before ones that
+ * were sent later.  As such, this function only does something
+ * if is the last one in the queue.
+ */
+static void pci_devices_present_work(struct work_struct *work)
+{
+       u32 child_no;
+       bool found;
+       struct list_head *iter;
+       struct pci_function_description *new_desc;
+       struct hv_pci_dev *hpdev;
+       struct hv_pcibus_device *hbus;
+       struct list_head removed;
+       struct hv_dr_work *dr_wrk;
+       struct hv_dr_state *dr = NULL;
+       unsigned long flags;
+
+       dr_wrk = container_of(work, struct hv_dr_work, wrk);
+       hbus = dr_wrk->bus;
+
+       INIT_LIST_HEAD(&removed);
+
+       if (down_interruptible(&hbus->enum_sem))
+               return;
+
+       /* Pull this off the queue and process it if it was the last one. */
+       spin_lock_irqsave(&hbus->device_list_lock, flags);
+       while (!list_empty(&hbus->dr_list)) {
+               dr = list_first_entry(&hbus->dr_list, struct hv_dr_state,
+                                     list_entry);
+               list_del(&dr->list_entry);
+
+               /* Throw this away if the list still has stuff in it. */
+               if (!list_empty(&hbus->dr_list))
+                       kfree(dr);
+               }
+
+               if (dr == NULL) {
+                       spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+                       goto present_exit;
+               }
+
+               /* First, mark all existing children as reported missing. */
+               list_for_each(iter, &hbus->children) {
+                       hpdev = container_of(iter, struct hv_pci_dev,
+                                            list_entry);
+                       hpdev->reported_missing = true;
+               }
+               spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+               /* Next, add back any reported devices. */
+               for (child_no = 0; child_no < dr->device_count; child_no++) {
+
+                       found = false;
+                       new_desc = &dr->func[child_no];
+
+                       spin_lock_irqsave(&hbus->device_list_lock, flags);
+                       list_for_each(iter, &hbus->children) {
+                               hpdev = container_of(iter, struct hv_pci_dev,
+                                                    list_entry);
+
+                               if ((hpdev->desc.s_no.slot ==
+                                    new_desc->s_no.slot) &&
+                                   (hpdev->desc.v_id == new_desc->v_id) &&
+                                   (hpdev->desc.d_id == new_desc->d_id) &&
+                                   (hpdev->desc.ser == new_desc->ser)) {
+                                       hpdev->reported_missing = false;
+                                       found = true;
+                               }
+                       }
+                       spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+               if (!found) {
+
+                       hpdev = new_pcichild_device(hbus, new_desc);
+                       if (!hpdev) {
+                               pr_err("couldn't record a child device.\n");
+                               goto present_exit;
+                       }
+               }
+       }
+
+       /* Move missing children to a list on the stack. */
+       spin_lock_irqsave(&hbus->device_list_lock, flags);
+       do {
+               found = false;
+               list_for_each(iter, &hbus->children) {
+                       hpdev = container_of(iter, struct hv_pci_dev,
+                                            list_entry);
+                       if (hpdev->reported_missing) {
+                               found = true;
+                               hv_pcichild_dec(hpdev, hv_pcidev_ref_childlist);
+                               list_del(&hpdev->list_entry);
+                               list_add_tail(&hpdev->list_entry, &removed);
+                               break;
+                       }
+               }
+       } while (found);
+       spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+present_exit:
+
+       /* Delete everything that should no longer exist. */
+       while (!list_empty(&removed)) {
+               hpdev = list_first_entry(&removed, struct hv_pci_dev,
+                                        list_entry);
+               list_del(&hpdev->list_entry);
+               hv_pcichild_dec(hpdev, hv_pcidev_ref_initial);
+       }
+
+       /* Tell the core to rescan bus because there may have been changes. */
+       if (hbus->state == hv_pcibus_installed) {
+               pci_lock_rescan_remove();
+               pci_scan_child_bus(hbus->pci_bus);
+               pci_unlock_rescan_remove();
+       } else {
+               survey_child_resources(hbus);
+       }
+
+       up(&hbus->enum_sem);
+       hv_pcibus_dec(hbus);
+
+       if (dr)
+               kfree(dr);
+       kfree(dr_wrk);
+}
+
+/**
+ * This function is invoked whenever a new list of devices for
+ * this bus appears.
+ */
+static void hv_pci_devices_present(struct hv_pcibus_device *hbus,
+                                  struct pci_bus_relations *relations)
+{
+       struct hv_dr_state *dr;
+       struct hv_dr_work *dr_wrk;
+       unsigned long flags;
+
+       dr_wrk = kzalloc(sizeof(struct hv_dr_work), GFP_NOWAIT);
+
+       if (!dr_wrk)
+               goto pci_devices_present_error;
+
+       dr = kzalloc(offsetof(struct hv_dr_state, func) +
+                    (sizeof(struct pci_function_description) *
+                     (relations->device_count)), GFP_NOWAIT);
+
+       if (!dr)  {
+               kfree(dr_wrk);
+               goto pci_devices_present_error;
+       }
+
+       INIT_WORK(&dr_wrk->wrk, pci_devices_present_work);
+       dr_wrk->bus = hbus;
+       dr->device_count = relations->device_count;
+       if (dr->device_count != 0) {
+               memcpy(dr->func, relations->func,
+                      sizeof(struct pci_function_description) *
+                      dr->device_count);
+       }
+
+       spin_lock_irqsave(&hbus->device_list_lock, flags);
+       list_add_tail(&dr->list_entry, &hbus->dr_list);
+       spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+       hv_pcibus_inc(hbus);
+       schedule_work(&dr_wrk->wrk);
+       return;
+
+pci_devices_present_error:
+       pr_err("Couldn't allocate memory to process new device list\n");
+}
+
+/**
+ * These functions handle ejecting a device.  Windows will
+ * attempt to gracefully eject a device, waiting 60 seconds to
+ * hear back from the guest OS that this completed successfully.
+ * If this timer expires, the device will be forcibly removed.
+ */
+static void hv_eject_device_work(struct work_struct *work)
+{
+       struct pci_eject_response *ejct_pkt;
+       struct hv_pci_dev *hpdev;
+       struct pci_dev *pdev;
+       unsigned long flags;
+       struct {
+               struct pci_packet pkt;
+               u8 buffer[sizeof(struct pci_eject_response) -
+                         sizeof(struct pci_message)];
+       } ctxt;
+
+       hpdev = container_of(work, struct hv_pci_dev, wrk);
+
+       if (hpdev->state != hv_pcichild_ejecting) {
+               hv_pcichild_dec(hpdev, hv_pcidev_ref_pnp);
+               return;
+       }
+
+       pdev = pci_get_domain_bus_and_slot(hpdev->hbus->sysdata.domain, 0,
+                                         slot_to_devfn(hpdev->desc.s_no.slot));
+       if (pdev) {
+               pci_dev_get(pdev);
+               pci_stop_and_remove_bus_device(pdev);
+               pci_dev_put(pdev);
+       }
+
+       memset(&ctxt, 0, sizeof(ctxt));
+       ejct_pkt = (struct pci_eject_response *)&ctxt.pkt.message;
+       ejct_pkt->message_type = PCI_EJECTION_COMPLETE;
+       ejct_pkt->slot.slot = hpdev->desc.s_no.slot;
+       vmbus_sendpacket(hpdev->hbus->hdev->channel, ejct_pkt,
+                        sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
+                        VM_PKT_DATA_INBAND, 0);
+
+       spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);
+       list_del(&hpdev->list_entry);
+       spin_unlock_irqrestore(&hpdev->hbus->device_list_lock, flags);
+
+       hv_pcichild_dec(hpdev, hv_pcidev_ref_childlist);
+       hv_pcichild_dec(hpdev, hv_pcidev_ref_pnp);
+       hv_pcibus_dec(hpdev->hbus);
+}
+
+static void hv_pci_eject_device(struct hv_pci_dev *hpdev)
+{
+       hpdev->state = hv_pcichild_ejecting;
+       hv_pcichild_inc(hpdev, hv_pcidev_ref_pnp);
+       INIT_WORK(&hpdev->wrk, hv_eject_device_work);
+       hv_pcibus_inc(hpdev->hbus);
+       schedule_work(&hpdev->wrk);
+}
+
+/**
+ * This function is invoked whenever the host sends a packet to
+ * this channel (which is private to this root PCI bus).
+ *
+ * @param context - The bus tracking struct.
+ */
+static void hv_pci_onchannelcallback(void *context)
+{
+       const int packet_size = 0x100;
+       int ret;
+       struct hv_pcibus_device *hbus = context;
+       u32 bytes_recvd;
+       u64 req_id;
+       struct vmpacket_descriptor *desc;
+       unsigned char *buffer;
+       int bufferlen = packet_size;
+       struct pci_packet *comp_packet;
+       struct pci_response *response;
+       struct pci_incoming_message *new_message;
+       struct pci_bus_relations *bus_rel;
+       struct pci_dev_inval_block *inval;
+       struct pci_dev_incoming *dev_message;
+       struct hv_pci_dev *hpdev;
+
+       buffer = kmalloc(bufferlen, GFP_ATOMIC);
+       if (!buffer)
+               return;
+
+       do {
+       ret = vmbus_recvpacket_raw(hbus->hdev->channel, buffer, bufferlen,
+                                  &bytes_recvd, &req_id);
+
+       switch (ret) {
+       case 0:
+               /*
+                * All incoming packets must be at least as large as a
+                * response.
+                */
+               if (bytes_recvd <= sizeof(struct pci_response)) {
+                       kfree(buffer);
+                       return;
+               }
+               desc = (struct vmpacket_descriptor *)buffer;
+
+               switch (desc->type) {
+               case VM_PKT_COMP:
+
+                       /*
+                        * The host is trusted, and thus its safe to interpret
+                        * this transaction ID as a pointer.
+                        */
+                       comp_packet = (struct pci_packet *)req_id;
+                       response = (struct pci_response *)buffer;
+                       comp_packet->completion_func(comp_packet->compl_ctxt,
+                                                    response,
+                                                    bytes_recvd);
+                       kfree(buffer);
+                       return;
+
+               case VM_PKT_DATA_INBAND:
+
+                       new_message = (struct pci_incoming_message *)buffer;
+                       switch (new_message->message_type.message_type) {
+                       case PCI_BUS_RELATIONS:
+
+                               bus_rel = (struct pci_bus_relations *)buffer;
+                               if (bytes_recvd <
+                                   offsetof(struct pci_bus_relations, func) +
+                                   (sizeof(struct pci_function_description) *
+                                    (bus_rel->device_count))) {
+
+                                       pr_err("bus relations too small\n");
+                                       break;
+                               }
+
+                               hv_pci_devices_present(hbus, bus_rel);
+                               break;
+
+                       case PCI_INVALIDATE_BLOCK:
+
+                               inval = (struct pci_dev_inval_block *)buffer;
+                               hpdev = lookup_hv_pcidev(hbus,
+                                                        inval->slot.slot);
+                               if (hpdev) {
+                                       if (hpdev->block_invalidate) {
+                                               hpdev->block_invalidate(
+                                                   hpdev->invalidate_context,
+                                                   inval->block_mask);
+                                       }
+                                       hv_pcichild_dec(hpdev,
+                                                       hv_pcidev_ref_by_slot);
+                               }
+                               break;
+
+                       case PCI_EJECT:
+
+                               dev_message = (struct pci_dev_incoming *)buffer;
+                               hpdev = lookup_hv_pcidev(hbus,
+                                                       dev_message->slot.slot);
+                               if (hpdev) {
+                                       hv_pci_eject_device(hpdev);
+                                       hv_pcichild_dec(hpdev,
+                                                       hv_pcidev_ref_by_slot);
+                               }
+                               break;
+
+                       default:
+                               pr_warn("Unimplemented protocol message %x\n",
+                                       new_message->message_type.message_type);
+                               break;
+                       }
+               break;
+
+               default:
+               pr_err("unhandled packet type %d, tid %llx len %d\n",
+                       desc->type, req_id, bytes_recvd);
+               break;
+               }
+
+               break;
+
+       case -ENOBUFS:
+               kfree(buffer);
+               /* Handle large packet */
+               bufferlen = bytes_recvd;
+               buffer = kmalloc(bytes_recvd, GFP_ATOMIC);
+               if (!buffer)
+                       return;
+
+               break;
+       }
+       } while (1);
+}
+
+/**
+ * This driver is intended to support running on Windows 10
+ * (server) and later versions.  It will not run on earlier
+ * versions, as they assume that many of the operations which
+ * Linux needs accomplished with a spinlock held were done via
+ * asynchronous messaging via VMBus.  Windows 10 increases the
+ * surface area of PCI emulation so that these actions can take
+ * place by suspending a virtual processor for their duration.
+ *
+ * This function negotiates the channel protocol version,
+ * failing if the host doesn't support the necessary protocol
+ * level.
+ */
+static int hv_pci_protocol_negotiation(struct hv_device *hdev)
+{
+       struct pci_version_request *version_req;
+       struct hv_pci_compl comp_pkt;
+       struct pci_packet *pkt;
+       int ret;
+
+       /*
+        * Initiate the hand shake with the host and negotiate
+        * a version that the host can support. We start with the
+        * highest version number and go down if the host cannot
+        * support it.
+        */
+
+       pkt = kzalloc(sizeof(*pkt) + sizeof(*version_req), GFP_KERNEL);
+       if (!pkt)
+               return -ENOMEM;
+
+       init_completion(&comp_pkt.host_event);
+       pkt->completion_func = hv_pci_generic_compl;
+       pkt->compl_ctxt = &comp_pkt;
+       version_req = (struct pci_version_request *)&pkt->message;
+       version_req->message_type.message_type = PCI_QUERY_PROTOCOL_VERSION;
+       version_req->protocol_version = PCI_PROTOCOL_VERSION_CURRENT;
+
+       ret = vmbus_sendpacket(hdev->channel, version_req,
+                              sizeof(struct pci_version_request),
+                              (unsigned long)pkt, VM_PKT_DATA_INBAND,
+                              VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+       if (ret)
+               goto protocol_exit;
+
+       wait_for_completion(&comp_pkt.host_event);
+
+       if (comp_pkt.completion_status < 0) {
+               pr_err("PCI Pass-through VSP failed version request %x\n",
+                      comp_pkt.completion_status);
+               ret = -EPROTO;
+               goto protocol_exit;
+       }
+
+       ret = 0;
+
+protocol_exit:
+
+       kfree(pkt);
+       return ret;
+}
+
+static void hv_pci_free_bridge_windows(struct hv_pcibus_device *hbus)
+{
+       if (hbus->low_mmio_space && hbus->low_mmio_res)
+               release_mem_region(hbus->low_mmio_res->start,
+                                  hbus->low_mmio_res->end -
+                                       hbus->low_mmio_res->start + 1);
+
+       if (hbus->high_mmio_space && hbus->high_mmio_res)
+               release_mem_region(hbus->high_mmio_res->start,
+                                  hbus->high_mmio_res->end -
+                                       hbus->high_mmio_res->start + 1);
+}
+
+static int hv_pci_allocate_bridge_windows(struct hv_pcibus_device *hbus)
+{
+       resource_size_t align;
+       int ret;
+
+       if (hbus->low_mmio_space) {
+               align = 1 << (63-__builtin_clzll(hbus->low_mmio_space));
+               ret = vmbus_allocate_mmio(&hbus->low_mmio_res, hbus->hdev, 0,
+                                         (u64)(u32)0xffffffff,
+                                         hbus->low_mmio_space,
+                                         align, false);
+               if (ret)
+                       return ret;
+
+               hbus->low_mmio_res->flags |= IORESOURCE_WINDOW;
+               hbus->low_mmio_res->flags &= ~IORESOURCE_BUSY;
+               pci_add_resource(&hbus->resources_for_children,
+                                hbus->low_mmio_res);
+       }
+
+
+       if (hbus->high_mmio_space) {
+               align = 1 << (63-__builtin_clzll(hbus->high_mmio_space));
+               ret = vmbus_allocate_mmio(&hbus->high_mmio_res, hbus->hdev,
+                                         0x100000000, -1,
+                                         hbus->high_mmio_space, align,
+                                         false);
+               if (ret)
+                       goto release;
+
+               hbus->high_mmio_res->flags |= IORESOURCE_WINDOW;
+               hbus->high_mmio_res->flags &= ~IORESOURCE_BUSY;
+               pci_add_resource(&hbus->resources_for_children,
+                                hbus->high_mmio_res);
+       }
+
+       return 0;
+
+release:
+
+       hv_pci_free_bridge_windows(hbus);
+       return ret;
+}
+
+static int hv_pci_d0_entry(struct hv_device *hdev)
+{
+       struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
+       struct pci_bus_d0_entry *d0_entry;
+       struct hv_pci_compl comp_pkt;
+       struct pci_packet *pkt;
+       int ret;
+
+       /*
+        * Tell the host that the bus is ready to use, and moved into the
+        * powered-on state.  This includes telling the host which region
+        * of memory-mapped I/O space has been chosen for configuration space
+        * access.
+        */
+
+       pkt = kzalloc(sizeof(*pkt) + sizeof(*d0_entry), GFP_KERNEL);
+       if (!pkt)
+               return -ENOMEM;
+
+       init_completion(&comp_pkt.host_event);
+       pkt->completion_func = hv_pci_generic_compl;
+       pkt->compl_ctxt = &comp_pkt;
+       d0_entry = (struct pci_bus_d0_entry *)&pkt->message;
+       d0_entry->message_type.message_type = PCI_BUS_D0ENTRY;
+       d0_entry->mmio_base = hbus->mem_config->start;
+
+       ret = vmbus_sendpacket(hdev->channel, d0_entry, sizeof(*d0_entry),
+                              (unsigned long)pkt, VM_PKT_DATA_INBAND,
+                              VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+       if (ret)
+               goto d0_entry_exit;
+       wait_for_completion(&comp_pkt.host_event);
+
+       if (comp_pkt.completion_status < 0) {
+               pr_err("PCI Pass-through VSP failed D0 Entry with status %x\n",
+                      comp_pkt.completion_status);
+               ret = -EPROTO;
+               goto d0_entry_exit;
+       }
+
+       ret = 0;
+
+d0_entry_exit:
+
+       kfree(pkt);
+       return ret;
+}
+
+static int hv_pci_query_relations(struct hv_device *hdev)
+{
+       struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
+       struct pci_message message;
+       struct completion comp;
+       int ret;
+
+       /*
+        * Ask the host to send along the list of child devices.
+        */
+
+       init_completion(&comp);
+       if (!cmpxchg(&hbus->survey_event, NULL, &comp)) {
+               memset(&message, 0, sizeof(message));
+               message.message_type = PCI_QUERY_BUS_RELATIONS;
+
+               ret = vmbus_sendpacket(hdev->channel, &message, sizeof(message),
+                                      0, VM_PKT_DATA_INBAND, 0);
+               if (ret)
+                       return ret;
+
+               wait_for_completion(&comp);
+               return 0;
+       } else
+               return -ENOTEMPTY;
+}
+
+/**
+ * The host OS is expecting to be sent a request as a message
+ * which contains all the resources that the device will use.
+ * The response contains those same resources, "translated"
+ * which is to say, the values which should be used by the
+ * hardware, when it delivers an interrupt.  (MMIO resources
+ * are used in local terms.)  This is nice for Windows, and
+ * lines up with the FDO/PDO split, which doesn't exist in
+ * Linux.  Linux is deeply expecting to scan an emulated PCI
+ * configuration space.  So this message is sent here only to
+ * drive the state machine on the host forward.
+ *
+ * @param hdev - The device associated with this virtual PCI
+ *             front-end
+ *
+ * @return int
+ */
+static int hv_send_resources_allocated(struct hv_device *hdev)
+{
+       struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
+       struct pci_resources_assigned *res_assigned;
+       struct hv_pci_compl comp_pkt;
+       struct hv_pci_dev *hpdev;
+       struct pci_packet *pkt;
+       u32 slot;
+       int ret;
+
+       pkt = kmalloc(sizeof(*pkt) + sizeof(*res_assigned), GFP_KERNEL);
+       if (!pkt)
+               return -ENOMEM;
+
+       for (slot = 0; slot < 256; slot++) {
+               hpdev = lookup_hv_pcidev(hbus, slot);
+               if (hpdev) {
+                       memset(pkt, 0, sizeof(*pkt) + sizeof(*res_assigned));
+                       init_completion(&comp_pkt.host_event);
+                       pkt->completion_func = hv_pci_generic_compl;
+                       pkt->compl_ctxt = &comp_pkt;
+                       pkt->message.message_type = PCI_RESOURCES_ASSIGNED;
+                       res_assigned =
+                               (struct pci_resources_assigned *)&pkt->message;
+                       res_assigned->slot.slot = hpdev->desc.s_no.slot;
+
+                       hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+
+                       ret = vmbus_sendpacket(
+                               hdev->channel, &pkt->message,
+                               sizeof(*res_assigned),
+                               (unsigned long)pkt,
+                               VM_PKT_DATA_INBAND,
+                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+                       if (ret)
+                               goto send_resources_allocated_free;
+
+                       wait_for_completion(&comp_pkt.host_event);
+
+                       if (comp_pkt.completion_status < 0) {
+                               ret = -EPROTO;
+                               pr_err("resource allocated returned 0x%x",
+                                      comp_pkt.completion_status);
+                               goto send_resources_allocated_free;
+                       }
+               }
+       }
+       ret = 0;
+
+send_resources_allocated_free:
+
+       kfree(pkt);
+       return ret;
+}
+
+static int hv_send_resources_released(struct hv_device *hdev)
+{
+       struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
+       struct pci_child_message pkt;
+       struct hv_pci_dev *hpdev;
+       u32 slot;
+       int ret;
+
+       for (slot = 0; slot < 256; slot++) {
+               hpdev = lookup_hv_pcidev(hbus, slot);
+               if (hpdev) {
+                       memset(&pkt, 0, sizeof(pkt));
+                       pkt.message_type = PCI_RESOURCES_RELEASED;
+                       pkt.slot.slot = hpdev->desc.s_no.slot;
+
+                       hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+
+                       ret = vmbus_sendpacket(hdev->channel, &pkt,
+                                              sizeof(pkt), 0,
+                                              VM_PKT_DATA_INBAND, 0);
+                       if (ret)
+                               return ret;
+               }
+       }
+
+       return 0;
+}
+
+static void hv_pcibus_inc(struct hv_pcibus_device *hbus)
+{
+       atomic_inc(&hbus->remove_lock);
+}
+
+static void hv_pcibus_dec(struct hv_pcibus_device *hbus)
+{
+       if (atomic_dec_and_test(&hbus->remove_lock))
+               complete(&hbus->remove_event);
+}
+
+/**
+ * This function is called as part of the VMBus probe routine.
+ *
+ * @param hdev - VMBus representation of the device
+ * @param dev_id - Indentifies the device itself
+  *
+ * @return int
+ */
+static int hv_pci_probe(struct hv_device *hdev,
+                       const struct hv_vmbus_device_id *dev_id)
+{
+       struct hv_pcibus_device *hbus;
+       int ret;
+
+       hbus = devm_kzalloc(&hdev->device, sizeof(*hbus), GFP_KERNEL);
+       if (!hbus)
+               return -ENOMEM;
+
+       pr_devel("New virtual PCIe bus: %p\n", hbus);
+
+       hbus->hdev = hdev;
+       INIT_LIST_HEAD(&hbus->children);
+       INIT_LIST_HEAD(&hbus->dr_list);
+       INIT_LIST_HEAD(&hbus->resources_for_children);
+       spin_lock_init(&hbus->config_lock);
+       spin_lock_init(&hbus->device_list_lock);
+       sema_init(&hbus->enum_sem, 1);
+       init_completion(&hbus->remove_event);
+       hv_pcibus_inc(hbus);
+
+       /*
+        * The PCI bus "domain" is what is called "segment" in the
+        * ACPI and other specs.  Pull it from the instance ID,
+        * to get something unique.  Bytes 8 and 9 are what is used
+        * in Windows guests, so do the same thing for consistency.
+        */
+
+       hbus->sysdata.domain = hdev->dev_instance.b[9] |
+                              hdev->dev_instance.b[8] << 8;
+
+       ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
+                        hv_pci_onchannelcallback, hbus);
+       if (ret)
+               return ret;
+
+       hv_set_drvdata(hdev, hbus);
+
+       ret = hv_pci_protocol_negotiation(hdev);
+       if (ret)
+               goto probe_close;
+
+       /*
+        * Set up a region of MMIO space to use for accessing configuration
+        * space.
+        */
+       ret = vmbus_allocate_mmio(&hbus->mem_config, hdev, 0, -1,
+                                 PCI_CONFIG_MMIO_LENGTH, 0x1000, false);
+       if (ret)
+               goto probe_close;
+
+       hbus->mem_config->flags |= IORESOURCE_BUSY;
+       hbus->cfg_addr = ioremap(hbus->mem_config->start,
+                                PCI_CONFIG_MMIO_LENGTH);
+       if (!hbus->cfg_addr) {
+               pr_err("Unable to map a virtual address for config space\n");
+               ret = -ENOMEM;
+               goto probe_release;
+       }
+
+       ret = hv_pci_query_relations(hdev);
+       if (ret)
+               goto probe_unmap;
+
+       ret = hv_pci_d0_entry(hdev);
+       if (ret)
+               goto probe_unmap;
+
+       ret = hv_pci_allocate_bridge_windows(hbus);
+       if (ret)
+               goto probe_unmap;
+
+       ret = hv_send_resources_allocated(hdev);
+       if (ret)
+               goto probe_unmap;
+
+       prepopulate_bars(hbus);
+
+       hbus->state = hv_pcibus_probed;
+
+       ret = create_root_hv_pci_bus(hbus);
+       if (ret)
+               goto probe_free_windows;
+       return 0;
+
+probe_free_windows:
+       hv_pci_free_bridge_windows(hbus);
+probe_unmap:
+       iounmap(hbus->cfg_addr);
+probe_release:
+       release_mem_region(hbus->mem_config->start, PCI_CONFIG_MMIO_LENGTH);
+probe_close:
+       vmbus_close(hdev->channel);
+       return ret;
+}
+
+static int hv_pci_remove(struct hv_device *hdev)
+{
+       int ret;
+       struct hv_pcibus_device *hbus;
+       union {
+       struct pci_packet teardown_packet;
+               __u8 buffer[0x100];
+       } pkt;
+       struct pci_bus_relations relations;
+       struct hv_pci_compl comp_pkt;
+
+       hbus = hv_get_drvdata(hdev);
+
+       ret = hv_send_resources_released(hdev);
+       if (ret)
+               pr_err("Couldn't send resources released packet(s)\n");
+
+       memset(&pkt.teardown_packet, 0, sizeof(pkt.teardown_packet));
+       init_completion(&comp_pkt.host_event);
+       pkt.teardown_packet.completion_func = hv_pci_generic_compl;
+       pkt.teardown_packet.compl_ctxt = &comp_pkt;
+       pkt.teardown_packet.message.message_type = PCI_BUS_D0EXIT;
+
+       ret = vmbus_sendpacket(hdev->channel, &pkt.teardown_packet.message,
+                              sizeof(struct pci_message),
+                              (unsigned long)&pkt.teardown_packet,
+                              VM_PKT_DATA_INBAND,
+                              VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+       if (!ret)
+               wait_for_completion_timeout(&comp_pkt.host_event, 5*HZ);
+
+       if (hbus->state == hv_pcibus_installed) {
+               /* Remove the bus from PCI's point of view. */
+               pci_lock_rescan_remove();
+               pci_stop_root_bus(hbus->pci_bus);
+               pci_remove_root_bus(hbus->pci_bus);
+               pci_unlock_rescan_remove();
+       }
+
+       vmbus_close(hdev->channel);
+
+       /* Delete any children which might still exist. */
+       memset(&relations, 0, sizeof(relations));
+       hv_pci_devices_present(hbus, &relations);
+
+       iounmap(hbus->cfg_addr);
+       release_mem_region(hbus->mem_config->start, PCI_CONFIG_MMIO_LENGTH);
+       hv_pci_free_bridge_windows(hbus);
+       pci_free_resource_list(&hbus->resources_for_children);
+       hv_pcibus_dec(hbus);
+       wait_for_completion(&hbus->remove_event);
+       return 0;
+}
+
+static const struct hv_vmbus_device_id hv_pci_id_table[] = {
+       /* PCI Pass-through Class ID */
+       /* 44C4F61D-4444-4400-9D52-802E27EDE19F */
+       { HV_PCIE_GUID, },
+       { },
+};
+
+MODULE_DEVICE_TABLE(vmbus, hv_pci_id_table);
+
+static  struct hv_driver hv_pci_drv = {
+       .name = "hv_pci",
+       .id_table = hv_pci_id_table,
+       .probe = hv_pci_probe,
+       .remove =  hv_pci_remove,
+};
+
+static void exit_hv_pci_drv(void)
+{
+       vmbus_driver_unregister(&hv_pci_drv);
+       hyperv_uninstall_interrupt_translation();
+}
+
+static int __init init_hv_pci_drv(void)
+{
+       int ret;
+
+       hv_msi.setup_msi_irqs = hv_setup_msi_irqs;
+       hv_msi.compose_msi_msg = hv_compose_msi_msg;
+       hv_msi.teardown_msi_irqs = hv_teardown_msi_irqs;
+       hv_msi.restore_msi_irqs = hv_restore_msi_irqs;
+
+       /*
+        * Hook the MSI management functions so that interrupts can be
+        * remapped through the hypervisor.
+        */
+
+       hyperv_install_interrupt_translation(&hv_msi);
+
+       /* Register this driver with VMBus. */
+       ret = vmbus_driver_register(&hv_pci_drv);
+
+       if (ret < 0)
+               exit_hv_pci_drv();
+
+       return ret;
+}
+
+module_init(init_hv_pci_drv);
+module_exit(exit_hv_pci_drv);
+
+MODULE_DESCRIPTION("Hyper-V PCI");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 1903238..0acf9ff 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1269,4 +1269,22 @@ void hv_process_channel_removal(struct vmbus_channel 
*channel, u32 relid);
 
 extern __u32 vmbus_proto_version;
 
+/*
+ * Functions for passing data between SR-IOV PF and VF drivers.  The VF driver
+ * sends requests to read and write blocks.  Each block must be 128 bytes or
+ * smaller so that the host can guarantee a successful response.  (All
+ * intermediate buffers are preallocated.)  Optionally, the VF driver can
+ * register a callback function which will be invoked when the host says that
+ * one or more of the first 64 block IDs is "invalid" which means that the
+ * VF driver should reread them.
+ */
+#define CONFIG_BLOCK_SIZE_MAX 128
+int hv_read_config_block(struct pci_dev *dev, void *buf, int buf_len,
+                        int block_id, int *bytes_returned);
+int hv_write_config_block(struct pci_dev *dev, void *buf, int len,
+                         int block_id);
+int hv_register_block_invalidate(struct pci_dev *dev, void *context,
+                                void (*block_invalidate)(void *context,
+                                                         u64 block_mask));
+
 #endif /* _HYPERV_H */
-- 
1.9.1

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